Installation of the Differential Pressure Switch and Indicator (APS 3200)

TASK 49-91-21-400-002-A
Installation of the Differential Pressure Switch and Indicator (APS 3200)

WARNING: DO NOT TOUCH THE APU UNTIL IT IS SUFFICIENTLY COOL TO PREVENT BURNS WHEN YOU DO THE MAINTENANCE TASK(S).

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	Torque wrench: range to between 19 and 17 lbf.in (0.21 and 0.19 m.daN )

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.03FAB1)	Mineral Oil base Grease-- Vaseline or Petrolatum -

C. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
315AL, 316AR

D. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)
TASK 29-00-00-864-001-A	Put the Related Hydraulic System in the Depressurized Configuration before Maintenance Action
TASK 49-00-00-710-008-A	Operational Test of the APU
TASK 52-41-00-010-001-A	Open the APU Doors for Access
TASK 52-41-00-410-001-A	Close the APU Doors after Access
Differential Pressure Switch

3. Job Set-up
Subtask 49-91-21-860-050-A ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration.
(1) Make sure that the aircraft electrical circuits are energized (Ref. AMM TASK 24-41-00-861-002).
(2) On the panel 25VU, make sure that the APU MASTER SW pushbutton switch is off.
(3) Make sure that there is a warning notice in the cockpit to tell persons not to start the APU.
(4) Make sure that the hydraulic systems are depressurized (Ref. AMM TASK 29-00-00-864-001).
(5) Make sure that the access platform is in position below the APU compartment.
(6) Make sure that the APU access doors are open (Ref. AMM TASK 52-41-00-010-001).
(7) Make sure that the LIGHT control switch 11LJ is set to the on position.

Subtask 49-91-21-865-056-A ** ON A/C NOT FOR ALL

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	APU/APU/CTL	2KD	L42
121VU	APU/ECB/SPLY	1KD	L41

4. Procedure
Subtask 49-91-21-420-051-A ** ON A/C NOT FOR ALL

A. Installation of the Differential Pressure Switch and Indicator
(1) Apply Mineral Oil base Grease-- Vaseline or Petrolatum - (Material No.03FAB1) to the new packing (2) and (3).
(2) Install the new packing (2) and (3) on the differential pressure switch and indicator (5).
(3) Install the differential pressure switch and indicator (5) with the screws (4) on the gearbox.
(4) TORQUE the screws (4) to between 19 and 17 lbf.in (0.21 and 0.19 m.daN )

.
(5) Remove the CAP-BLANKING from each electrical connector and receptacle.
(6) Connect the electrical connector P5 (1) to the differential pressure switch and indicator (5).

Subtask 49-91-21-865-057-A ** ON A/C NOT FOR ALL

B. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	APU/APU/CTL	2KD	L42
121VU	APU/ECB/SPLY	1KD	L41

Subtask 49-91-21-710-052-A ** ON A/C NOT FOR ALL

C. Test
(1) Do the operational test of the APU (Ref. AMM TASK 49-00-00-710-008).
(a) Operate the APU for min. five minutes and examine the joints of the differential pressure switch and indicator for leaks.

NOTE: Leaks are not permitted.

5. Close-up
Subtask 49-91-21-410-052-A ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Set the LIGHT control switch 11LJ to the off position.
(3) Close the APU access doors 315AL 316AR (Ref. AMM TASK 52-41-00-410-001).
(4) Remove the access platform(s).

Subtask 49-91-21-860-052-A ** ON A/C NOT FOR ALL

B. Aircraft Maintenance Configuration.
(1) Put the related hydraulic system in the pressurized configuration (Ref. AMM TASK 29-00-00-864-001).
(2) De-energize the aircraft electrical circuits
(Ref. AMM TASK 24-41-00-862-002).
(3) Remove the WARNING NOTICE(S).

[Rev.10 from 2021] 2026.04.01 01:33:06 UTC